1. Field of the Invention
This invention relates to a disc loading structure, and more particularly to a disc loading structure which is adapted to properly accomplish an operation of loading a disc in a disc player such as a compact disc player, a laser disc player or the like.
2. Description of Related Art
Conventionally, a compact disc player for reproducing a digital signal recorded on a compact disc is provided with a disc loading structure for loading the player with the compact disc while holding it. For this purpose, a disc loading structure of the automatic loading type which is constructed as shown in FIGS. 1 and 2 is conventionally employed.
More particularly, the conventional disc loading structure includes a housing 20 and a turntable 22 rotatably arranged in the housing 20. The housing 20 is provided on the front side thereof with a disc port 24. Also, the disc loading structure includes a transfer roller 26 which is arranged so as to be rotatable in both directions and positioned between the turntable 22 and the disc port 24. When a disc 28 is to be loaded in a disc player, the disc 28 which is inserted through the disc port 24, as shown in FIG. 2, is vertically interposed between the transfer roller 26 and a support member 30 arranged vertically opposite to the transfer roller 26 in the housing 20. Then, the transfer roller 26 is rotated in one direction or a disc loading direction to transfer the disc 28 to a position above the turntable 22. In order to ensure that the disc 28 is accurately positioned above the turntable 22, a pair of positioning guide pins 32 are arranged at the rear section of a disc transfer passage defined in the housing 20. Such arrangement of the positioning pins 32 permits the peripheral edge of the disc 28 to be abutted against the pins 32 during the loading operation, to thereby align a central hole 34 of the disc 28 with the turntable 22. Then, the disc 28 is lowered onto the turntable 22 through a suitable, lifting means (not shown) such as a liftable clamping or chucking means. Then, the completion of operation of the chucking means is detected through a microswitch or the like, so that a drive motor (not shown) is stopped to stop the actuation of the transfer roller 26, resulting in the loading operation being completed.
As will be noted from the foregoing, in the conventional disc loading structure of the automatic loading type constructed as described above, the placing of the disc on the turntable for play-back merely requires the insertion of the disc through the disc port 24 into the structure. Thus, the disc loading structure exhibits excellent operability even under vibrating conditions, resulting in being used for a mounted-type disc player which is adapted to be mounted on a vehicle such as a car or the like.
However, the conventional disc loading structure fails to generate an ejection signal when a foreign article of a size smaller than a predetermined disc such as a credit card or the like is inserted through the disc port thereinto, so that it irreversibly enters the disc loading structure. This causes an internal mechanism of the disc player such as a pickup, a spindle or the like to be often damaged or failed. Thus, the conventional disc loading structure fails to distinguish a disc from a foreign article, leading to a failure in operation with reliability.
Recently, the demand on a compact disc by consumers is highly diversified with the rapid spread of the compact disc, leading to the manufacturing of a compact disc of a diameter as small as 8 cm (8 cm compact disc) which is called a single CD, in addition to an existing compact disc of 12 cm in diameter (12 cm compact disc). The 8 cm disc corresponds to an analog single disc of 17 cm in diameter. The appearance of the 8 cm disc causes some important problems. The conventional compact disc player is constructed so as to accommodate to only the existing 12 cm compact disc, to thereby fail to distinguish the 8 cm disc and 12 cm disc from each other. Therefore, the playing-back of the 8 cm compact disc requires to use an exclusive adapter therefor. Thus, when only the adapter for the 8 cm compact disc is erroneously inserted through the disc port, the disc loading structure causes it to irreversibly enter the structure while failing to generate an ejection signal, leading to a failure in the internal mechanism of the disc player. Thus, it will be noted that the conventional disc loading structure also fails to distinguish the compact disc from the adapter.
Further, the use of the exclusive adapter for the 8 cm disc renders the disc loading operation highly troublesome. In order to eliminate the problem, it is proposed that the disc loading structure is provided with a stopper arm for positioning a compact disc in place and holding it on a turntable. However, the conventional disc loading structure also fails to accurately discriminate discs of different sizes from each other during the disc loading operation.
In addition, it is proposed that the conventional disc loading structure is provided with a single sensor for detecting the completion of insertion of the disc 28. For this purpose, it is arranged between the disc port 24 and the transfer roller 26. Such a single sensor may comprise, for example, a photosensor arranged so as to be positioned slightly outside the outer periphery of the disc 28 when it is placed on the turntable 22. The single sensor is adapted to exhibit a detection mode when it detects that something obstructs it and exhibit a non-detection mode when there is nothing to obstruct it. Thus, when the sensor takes the detection mode and then exhibits the non-detection mode, the structure judges that the disc is placed on the turntable 22, to thereby detect the completion of insertion of the disc and start the chucking means, resulting in completing the loading. Unfortunately, such arrangement of the single sensor causes some disadvantages. More specifically, when there occurs any accident such as the insertion of a foreign article other than the compact disc into the structure, the lateral movement of the disc near the disc port, the drawing-out of the disc from the structure after slight insertion of the disc through the disc port thereinto, or the like which is sufficient to cause actuation of the sensor, the mode of the detection sensor is changed from the detection mode to the non-detection mode, to thereby cause the clamping or chucking means to uselessly carry out or repeat the disc clamping or chucking operation, resulting in the disc, the components of the structure and the like being damaged and/or failed.
It is widely known in the art that the above-described disadvantages are also encountered with various disc players in addition to the compact disc player.